This invention generally relates to a spraying apparatus for bombarding a workpiece with a jet of solid particles for the cleaning, descaling or similar handling of the workpiece. More particularly, the invention is concerned with a centrifugal wheel assembly which forms part of the spraying apparatus and which includes a disc-type guide wheel and impeller vanes affixed to the guide wheel. The particles of the material to be sprayed are guided by the impeller vanes in the radial direction, accelerated and propelled outwardly by centrifugal force. The impeller vanes are, due to the particles impinging thereon and due to their high speed, exposed to substantial wear necessitating their relatively frequent replacement.
It is conventional to structure the two opposite sides of each impeller vane identically so that either side is adapted to function selectively as the propelling surface for the material. Such a design, on the one hand, makes possible a drive of the centrifugal wheel assembly in either rotary direction and, on the other hand, permits a selective installation of each impeller vane at a 180.degree. inverted position with respect to the longitudinal axis of the impeller vane. It is a requisite in such structures that the impeller vanes be easily removable, that they be located at areas protected from wear and that their operationally safe immobilization (fixation) be ensured. In an arrangement disclosed in German Auslegeschrift (Accepted Published Patent Application) No. 2,606,063, the immobilization of the impeller vanes in the centrifugal wheel assembly is effected by an impeller foot of dovetail shape inserted into a complemental groove and is maintained in place by leaf springs. In a centrifugal wheel assembly disclosed in German Offenlegungsschrift (Laid-Open Application) No. 2,634,198, the immobilization of the impeller vanes is effected by cams which are provided in the reinforced longitudinal edges of the impeller wheels adjacent their ends and project into a slot provided in a disc-type guide wheel. The known centrifugal wheels can be installed and used only in the two selected positions as described above.